Using a sample of ∼28,000 sources selected at 3.6-4.5 microns with Spitzer observations of the HDF-N, the CDF-S, and the Lockman Hole (surveyed area: ∼664 arcmin 2 ), we study the evolution of the stellar mass content of the Universe at 0
We present the results of an Hα near-infrared narrow-band survey searching for star-forming galaxies at redshift z = 0.84. This work is an extension of our previous narrow-band studies in the optical at lower redshifts. After removal of stars and redshift interlopers (using spectroscopic and photometric redshifts), we build a complete sample of 165 Hα emitters in the Extended Groth strip and GOODS-N fields with L(Hα)>10 41 erg s −1 . We compute the Hα luminosity function at z = 0.84 after corrections for [NII] flux contamination, extinction, systematic errors, and incompleteness. Our sources present an average dust extinction of A(Hα)=1.5 mag. Adopting Hα as a surrogate for the instantaneous star formation rate (SFR), we measure a extinction-corrected SFR density of 0.17 +0.03 −0.03 M ⊙ yr −1 Mpc −3 . Combining this result to our prior measurements at z=0.02, 0.24, and 0.40, we derive an Hα-based evolution of the SFR density proportional to (1+z) β with β = 3.8 ± 0.5. This evolution is consistent with that derived by other authors using different SFR tracers.
We present the Survey for High-z Absorption Red and Dead Sources (SHARDS), an ESO/GTC Large Program carried out with the OSIRIS instrument on the 10.4m Gran Telescopio Canarias (GTC). SHARDS is an ultra-deep optical spectro-photometric survey of the GOODS-N field covering 130 arcmin 2 at wavelengths between 500 and 950 nm with 24 contiguous medium-band filters (providing a spectral resolution R∼50). The data reach an AB magnitude of 26.5 (at least at a 3σ level) with sub-arcsec seeing in all bands. SHARDS main goal is obtaining accurate physical properties of intermediate and high-z galaxies using well-sampled optical SEDs with sufficient spectral resolution to measure absorption and emission features, whose analysis will provide reliable stellar population and AGN parameters. Among the different populations of high-z galaxies, SHARDS principal targets are massive quiescent galaxies at z>1, whose existence is one of the major challenges of current hierarchical models of galaxy formation. In this paper, we outline the observational strategy and include a detailed discussion of the special reduction and calibration procedures which should be applied to the GTC/OSIRIS data. An assessment of the SHARDS data quality is also performed. We present science demonstration results about the detection and study of emission-line galaxies (star-forming objects and AGN) at z=0-5. We also analyze the SEDs for a sample of 27 quiescent massive galaxies with spectroscopic redshifts in the range 1.0
Based on the ultraviolet to far-infrared photometry already compiled and presented in a companion paper (Paper I), we present a detailed spectral energy distribution (SED) analysis of nearly 80,000 IRAC 3.6 + 4.5 μm selected galaxies in the Extended Groth Strip. We estimate photometric redshifts, stellar masses, and star formation rates (SFRs) separately for each galaxy in this large sample. The catalog includes 76,936 sources with [3.6] 23.75 (85% completeness level of the IRAC survey) over 0.48 deg 2 . The typical photometric redshift accuracy is Δz/(1 + z) = 0.034, with a catastrophic outlier fraction of just 2%. We quantify the systematics introduced by the use of different stellar population synthesis libraries and initial mass functions in the calculation of stellar masses. We find systematic offsets ranging from 0.1 to 0.4 dex, with a typical scatter of 0.3 dex. We also provide UV-and IR-based SFRs for all sample galaxies, based on several sets of dust emission templates and SFR indicators. We evaluate the systematic differences and goodness of the different SFR estimations using the deep FIDEL 70 μm data available in the Extended Groth Strip. Typical random uncertainties of the IR-bases SFRs are a factor of two, with non-negligible systematic effects at z 1.5 observed when only MIPS 24 μm data are available. All data products (SEDs, postage stamps from imaging data, and different estimations of the photometric redshifts, stellar masses, and SFRs of each galaxy) described in this and the companion paper are publicly available, and they can be accessed through our the Web interface utility Rainbow-navigator.
Abstract. We present a detailed and uniform study of C, S, Zn and Cu abundances in a large set of planet host stars, as well as in a homogeneous comparison sample of solar-type dwarfs with no known planetary-mass companions. Carbon abundances were derived by EW measurement of two C optical lines, while spectral syntheses were performed for S, Zn and Cu. We investigated possible differences in the behaviours of the volatiles C, S and Zn and in the refractory Cu in targets with and without known planets in order to check possible anomalies due to the presence of planets. We found that the abundance distributions in stars with exoplanets are the high [Fe/H]
We present an IRAC 3.6+4.5 µm selected catalog in the Extended Groth Strip (EGS) containing photometry from the ultraviolet to the far-infrared and stellar parameters derived from the analysis of the multi-wavelength data. In this paper, we describe the method used to build coherent spectral energy distributions (SEDs) for all the sources. In a companion paper, we analyze those SEDs to obtain robust estimations of stellar parameters such as photometric redshifts, stellar masses, and star formation rates. The catalog comprises 76,936 sources with [3.6]≤23.75 mag (85% completeness level of the IRAC survey in the EGS) over 0.48 deg 2 . For approximately 16% of this sample, we are able to deconvolve the IRAC data to obtain robust fluxes for the multiple counterparts found in groundbased optical images. Typically, the SEDs of the IRAC sources in our catalog count with more than 15 photometric data points, spanning from the ultraviolet wavelengths probed by GALEX to the farinfrared observed by Spitzer, and going through ground-and space-based optical and near-infrared data taken with 2-8 meter class telescopes. Approximately 95% and 90% of all IRAC sources are detected in the deepest optical and near-infrared bands. These fractions are reduced to 85% and 70% for SNR>5 detections in each band. Only 10% of the sources in the catalog have optical spectroscopy and redshift estimations. Almost 20% and 2% of the sources are detected by MIPS at 24 and 70 µm, respectively. We also cross-correlate our catalog with public X-ray and radio catalogs. Finally, we present the Rainbow Navigator public web-interface utility, designed to browse all the data products resulting from this work, including images, spectra, photometry, and stellar parameters.
We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z ∼ 1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in two hour exposures of 36 emission-line galaxies. We compare X-ray data with the traditional emission-line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [O iii]/Hβ ratio is insufficient as an AGN indicator at z > 1. For the four X-ray detected galaxies, the classic diagnostics ([O iii]/Hβ vs.[Nii]/Hα and [Sii]/Hα) remain consistent with X-ray AGN/SF classification. The X-ray data also suggest that "composite" galaxies (with intermediate AGN/SF classification) host bona-fide AGNs. Nearly ∼2/3 of the z ∼ 1.5 emission-line galaxies have nuclear activity detected by either X-rays or the classic diagnostics. Compared to the X-ray and line ratio classifications, the mass-excitation method remains effective at z > 1, but we show that the color-excitation method requires a new calibration to successfully identify AGNs at these redshifts.
Aims. Lyα emitters (LAEs) can be detected out to very high redshifts during the epoch of reionization. The evolution of the LAE luminosity function with redshift is a direct probe of the Lyα transmission of the intergalactic medium (IGM), and therefore of the IGM neutral-hydrogen fraction. Measuring the Lyα luminosity function (LF) of Lyα emitters at redshift z = 7.7 therefore allows us to constrain the ionizing state of the Universe at this redshift. Methods. We observed three 7. ′ 5×7. ′ 5 fields with the HAWK-I instrument at the VLT with a narrow band filter centred at 1.06 µm and targeting Lyα emitters at redshift z ∼ 7.7. The fields were chosen for the availability of multiwavelength data. One field is a galaxy cluster, the Bullet Cluster, which allowed us to use gravitational amplification to probe luminosities that are fainter than in the field. The two other fields are subareas of the GOODS Chandra Deep Field South and CFHTLS-D4 deep field. We selected z = 7.7 LAE candidates from a variety of colour criteria, in particular from the absence of detection in the optical bands. Results. We do not find any LAE candidates at z = 7.7 in ∼ 2.4 × 10 4 Mpc 3 down to a narrow band AB magnitude of ∼ 26, which allows us to infer robust constraints on the Lyα LAE luminosity function at this redshift. Conclusions. The predicted mean number of objects at z = 6.5, derived from somewhat different luminosity functions of Hu et al. (2010), Ouchi et al. (2010), and Kashikawa et al. (2011. Depending on which of these luminosity functions we refer to, we exclude a scenario with no evolution from z = 6.5 to z = 7.7 at 85% confidence without requiring a strong change in the IGM Lyα transmission, or at 99% confidence with a significant quenching of the IGM Lyα transmission, possibly from a strong increase in the high neutral-hydrogen fraction between these two redshifts.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.